The present invention relates to a method of manufacturing a shaped workpiece formed from a plastic material by welding a union, e.g., of a valve body, with a tubular part, wherein the end face surface of the union is welded to the circumference of the tubular part. The present invention also relates to an apparatus for effecting the inventive method.
A method of welding a union to an outer circumference of a tubular part is disclosed, e.g., in Swiss patent CH-PS 570-577. The Swiss patent discloses a method of welding a union for a branch conduit to an outer circumference of a pipe, according to which method a welding mat formed of a resistance wire is placed between the pipe and a union saddle to provide welding temperatures. However, this method of manufacturing of a shaped workpiece formed of a plastic material is very expensive.
Accordingly, an object of the invention is an improved method of welding of a union to a pipe, which would insure a strong welding connection, without using additional auxiliary means which, at that, forms part of the welding connection.
Another object of the invention is an apparatus for effecting the improved method.
Yet another object of the invention is a shaped workpiece manufactured by the improved method.